The present invention concerns a blow-off valve for a hydraulic dashpot.
Hydraulic dashpots are employed to absorb shock accompanying the motion of wheel suspensions attached by way of springs, preferably in motor vehicles. The shock is absorbed by forcing fluid through preferably spring-loaded ports in a piston from one compartment and into another in a fluid-charged cylinder.
When obstacles in the road are driven over rapidly, the absorption is high enough to introduce sudden forces into the suspension due to the dashpot operating too “hard”. The use of blow-off valves that respond and permit fluid to flow from the compartment more remote from the piston rod and into the compartment adjacent thereto is accordingly known from German 2 340 987. Such valves do not respond, however, while the dashpot is operating normally.
There are drawbacks to the blow-off system disclosed in German 2 340 987 A1. First, it is controlled by controls inside the piston rod. Again, the hydraulic blow-off flow also travels through the piston rod. Such an approach cannot be employed if the piston-rod bore also accommodates other controls and flow diverters or electric and pneumatic lines as in the embodiment known from German 10 138 487 C1 for example.